I wanted to try the Cursed Walking - a Modern Zombie Apocalypse modpack with Indev Hell world type to add extra challenge in the form of always nighttime, limited mobs and resources, and no structures. Modern Beta is a mod that provides old world generation from various outdated versions of Minecraft, one of which includes the Hell world type from Indev. I tried to make a Modern Beta Indev Hell world within the modpack, and the game crashed upon the beginning of the creation of the world. I disabled mods that I believed to be susceptible such as Eccologics, Phillips Ruins, Overworld Ancient Debris, Farmers Delight, and Lost Cities. I was able to load a Modern Beta type world with all of these mods enabled except for Lost Cities. The game crashes even when Cities are not enabled for the world.

Crash log - https://pastebin.com/MfK1uw9T

This looks like fabric? Lost Cities is a forge mod. Doesn't work on fabric

This looks like fabric? Lost Cities is a forge mod. Doesn't work on fabric

I forgot to mention that this is possible via Syntra Connector mod. However, there is now an unofficial Forge version of Modern Beta that I can try with. If the problem still persists with Lost Cities and Modern Beta Forge, then it is a problem on Lost Cities end as opposed to Syntra or Modern Beta.